Rectal Cancer Worsened by Oral Microbes, Research Indicates.

Could poor oral hygiene increase your risk for colorectal cancer? A new study suggests poor oral hygiene is connected to the health and well-being of yet another portion of the body. Colorectal cancer is the third most common cancer diagnosed in the United States, and the second most deadly, especially if regular screening for precancerous polyps is not regularly conducted.

Studies by the Garret Lab at Harvard have shown fusobacteria when present in the colon in high concentrations increase the risk of an individual for colon cancer. Fusobacteria are primarily oral pathogens which have been found to cause periodontal disease and ulcers. Furthermore, cancerous tissue in the colon has been found to be enriched with fusobacterium compared to surrounding, healthy tissue. This suggests that the bacteria are localizing somehow to the cancerous region in the colon from the mouth. But how?

One study from researchers at Hebrew University School of Dental Medicine attempted to discern this. Since it is well-established that oral bacteria can reach the bloodstream through bleeding gingiva or root tips, the researchers decided to inject a fusobacterial culture into the bloodstream and chemically track their movement. The bacteria were injected through a tail vein into two types of mouse; one group with precancerous colon growths, and the other with malignant colon cancer. After a brief waiting period, the colons of both groups were dissected and analyzed using fluoroscopy. The researchers found that the fusobacteria adhered in large quantities to both groups of tumors, and were not present in any heightened quantity in the control group. Furthermore, for the precancerous and cancerous group, the livers of both were found to have high concentrations of fusobacteria compared to the control. Colon cancer frequently metastasizes to the liver, and it is interesting that this seems to be pre-empted by the bacteria, suggesting a possible bacterial precursor or correlation to the metastatic process. This could prove highly useful in trying to predict or prevent the progression of colon cancer.

So what draws the bacteria to the tumor? Well, from studying a combination of human samples and mouse-model experiments, it appears a protein on the surface coat of the fusobacteria have a protein called Fap2 that binds to the sugar Gal-Gal-Nac, found in high concentrations on colorectal tumor cells. The protein Fap2 appears to mediate the colonization of tumor cells by the bacteria, and may represent a potential target for therapy. In any event, maintaining good oral hygiene and promptly seeing a dentist to address any infections in the mouth is reinforced by these findings.